Projectile sabot

ABSTRACT

A sleeve assembly, to be referred to as a sabot, is to surround a projectile within an oversized bore of the barrel of a firearm. The sabot is formed of a first set and a second set of half shells with the second set to surround the first set in the aft section of the projectile, both sets to be discarded after the projectile leaves the bore. The material of construction of the first set is to have characteristics of high strength and substantially no elasticity. The material of construction of the second set is to have characteristics of high strength and relative elasticity. The aft surface area of the second set is to comprise approximately 50 percent of the total aft surface area.

United States Patent [151 Witherspoon et al.

Oct. 2, 1973 1 PROJECTILE SABOT [76] Inventors: Linton S. Wither-spoon, 7216 Butte Dr., Goleta; Robert 11. Dunlap, 6165 Second Ave., Sacramento, both of Calif.

[22] Filed: July 8, 1971 [21] Appl. No.: 160,604

[52] U.S. Cl. 102/94 [51] Int. Cl. F42b 13/16 [58] Field of Search 102/93, 94

[56] References Cited UNITED STATES PATENTS 2,613,372 11/1952 Frantik 102/93 2,306,140 12/1942 Reed 3,005,408 10/1961 Prosen et al. 102/93 Primary ExaminerRobert F. Stahl Al!0rneyRobert E. Geauque [57] ABSTRACT A sleeve assembly, to be referred to as a sabot, is to surround a projectile within an oversized bore of the barrel of a firearm. The sabot is formed of a first set and a second set of half shells with the second set to surround the first set in the aft section of the projectile, both sets to be discarded after the projectile leaves the bore. The material of construction of the first set is to have characteristics of high strength and substantially no elasticity. The material of construction of the second set is to have characteristics of high strength and relative elasticity. The aft surface area of the second set is to comprise approximately 50 percent of the total aft surface area.

10 Claims, 7 Drawing Figures PATENTED 21975 3.762.332

l NVENTOR.

BY WW PROJECTILE SABOT BACKGROUND OF THE INVENTION Within the military the word sabot refers to a sleeve which is to be placed around a projectile prior to being propelled by a firearm such as smooth bore cannon. A discarding sabot is a supporting sleeve that is used for firing projectiles from gun barrels which have a bore diameter larger than the projectile diameter. The sabot transmits accelerating forces and spinning motion to the projectile and guides it symmetrically through the barrel. Upon leaving the barrel, the sabot separates from the projectile either radially by centrifugal forces or longitudinally by drag differential forces. Sabots are usually made of plastic, aluminum, or some other low density material. The main advantage of using a discarding sabot is that projectiles of more efficient ballistic shape may be fired from conventional guns with an increase in exterior ballistic performance. Exterior ballistic performance can be defined as trajectory characteristics of the projectile after leaving the gun barrel. Interior ballistic performance is concerned with the firing characteristics within the bore of the gun.

There are several types of sabots currently being employed. Generally, discarding sabots are classified as either push type or pull type. The push type is where the projectile is accelerated by means of applying force to the rear surface of the projectile. The pull type is where the projectile is pulled by the sabot by applying longitudinal forces on a forward contour or shoulder of the projectile or by longitudinal friction along the sides of the projectile.

Upon exit from the gun barrel, the discarding sabot separates permitting the projectile to fly to its target as accurately as possible. There are currently employed three methods used in separating the sabot. The first method is by the use of aerodynamic drag differential. The sabot is cupshaped and when the projectile and sabot leaves the bore of the gun, the projectile slides out of the cup due to higher stagnation pressure on the flat forward pressure of the cup.

The second and most-widely used method is to utilize the centrifugal forces produced by the rifling twist of the gun. Within this method the sabot usually has longitudinal slots which are placed at equal locations around the circumference. When the projectile leaves the muzzle and is no longer confined, the sabot tears into equal segments which separate radially. In some designs the sabot is made initially into a number of parts resembling petals. In this instance, the neck of the cartridge case holds the petals together before firing.

The third method of separation is a combination of the former two methods. The aft portion of the projectile is engulfed in an aluminum cup which drag separates and the forward portion of the cup is engulfed in a slotted plastic cylinder which tears apart upon release from the barrel.

Heretofore, discarding sabots have been commonly employed with armor piercing bullets which have a steel or some other high strength metallic core. In such situations, there is no problem of projectile overstress and the only use of the sabot has been to launch the projectile accurately.

To launch ajacketed lead bullet presents a new problem. The lead has a very low compressive strength and until now could not be launched with a discarding sabot without deformation. Due to the acceleration stresses within the bore of the gun, the soft lead is caused to move toward the base of the projectile causing the base to swell to a much larger diameter. The conventional plastic sabot is not capable of supporting the circumference of the projectile as the gun barrel does with the normal bore sized projectile. The results of the deformated projectile are a loss of accuracy and a drastic increase in aerodynamic drag.

SUMMARY OF THE INVENTION The sabot of this invention is designed to employ the mechanical advantage of a wedge to launch a lead projectile and prevent the base of the projectile from enlarging during acceleration of such within the bore of a gun. The sabot is composed of two separate sections with each section being composed of two half shell elements. This separating of the sections into separate elements facilitates discarding of the shells after exit from the bore of a gun. The shells of the first section are to have a substantially cylindrical shaped forward part with the aft part being tapered into a conical configuration. The second'section of half shells is to cooperate about the first section of half shells in a mating manner with the conical section of the first set of half shells. The first set of half shells is to be made of a material of construction having extremely high strength characteristics and which also is substantially non-elastic. The second set of half shells is to be formed of a material which also has high strength characteristics but compared with the material of the first set has substantially more elasticity. In other words, the material of the second section is to be readily deformable as compared to the material of the first section. The aft surface area of the second set of shells is to comprise approximately 50 percent of the entire aft surface area. The expanding gases, upon the firing of the cartridge, force the projectile and surrounding sabot forward through the gun barrel. Because of the conical wedging arrangement between the first section and the second section, radial forces are transmitted from the second section through the aft part of the first section and against the aft portion of the projectile. The area arrangement is such so that the inward radial forces overcome the tendency for the copper jacketed lead bullet to expand at its base. Thus, the projectile is fullysupported just as the barrel of a gun reacts to a projectile for which it is designed.

An advantage of employing the sabot of this invention is that the copper jacketed lead bullet receives no rifling marks therein thereby reducing aerodynamic drag and improving flight performance of the projectile.

Another significant advantage of the sabot of this invention is that larger bore guns become more versatile to hunters and target shooters. This will especially benefit shooters who cannot afford a special gun for every occasion.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall view of a cartridge and its associated projectile to which is connected the first embodiment of the sabot of this invention;

FIG. 2 is an enlarged cross-sectional view of the first embodiment of the sabot of this invention taken along line 2-2 of FIG. 1;

FIG. 3 is a view of the base and aft edge of the sabot taken along line 33 of FIG. 2;

FIG. 4 is a partially cut-away, fragmentary, crosssectional view depicting the sabot and projectile during passage through the barrel of a gun;

FIG. 5 is a diagrammatic representation of the first embodiment of the sabot of this invention showing such being discarded upon the projectile leaving the barrel of the gun;

FIG. 6 is a cross-sectional view of the second embodi ment of this invention; and

FIG. 7 is a view of the base of the projectile and associated sabot taken along line 77 of FIG. 6.

DETAILED DESCRIPTION OF THE SHOWN EMBODIMENTS Referring particularly to the drawing, there is shown in FIG. 1 a cartridge 10 being composed of a cartridge case 12, a sabot 14 of this invention, and a projectile 16. The cartridge case 12 has a neck 18 which is adapted to surround and retain the sabot l4 and its associated projectile 16. It is to be understood that the cartridge 10 is to be capable of being placed within a gun (not shown) and, upon being fired, the sabot l4 and its associated projectile 16 are to be conducted through the bore 20 of a gun barrel 22, as shown in FIG. 4 of the drawing.

Sabot 14 of the first embodiment of this invention is divided into a first set 24 and a second set 26. The first set 24 is composed of two half shell elements 28 and 30. Each of the elements 28 and 30 are formed identical to each other and have a substantially cylindrical forward section and a conically tapered aft section. Annular recess 32 separates the forward section from the aft section.

The first set 24 of half shells must be capable of withstanding the expanding gases within the bore 20 and it is also desirable that the material of construction of the first set 24 not affected by the lands 34 formed within the bore 20. For this reason, the desirable type of material for the first set 24 is an extremely high strength glass fiber reinforced plastic. This material should also be substantially non-elastic, in other words, extremely hard.

The second set 26 is composed of identical half shell elements 36 and 38. Each of the elements 36 and 38 includes a conical interior bore 40. The bore 40 of each of the elements 36 and 38 is adapted to come into contact with the conically outer surface of the elements 28 and 30 of the first set 24. A lip 42 is formed at the front edge of each of the elements 36 and 38 and is adapted to matingly cooperate within the recess 32. The lip 42 functions in cooperation with the recess 32 so as to prevent longitudinal slipping of the elements 36 and 38 away from the elements 28 and 30 during handling and storage while in the assembled condition.

The elements 36 and 38 are to be similarly constructed of a high strength material which will not fracture during firing of the cartridge 10. However, it is desired that the elements 36 and 38 be formed of a material with a certain amount of resiliency so as to be deformed by the lands 34. This deformation by the lands 34 functions to effect a spinning of the projectile 16 and its associated sabot 14 upon exit from the muzzle of the barrel 22. A desirable material of construction of the elements 36 and 38 is a polycarbonate plastic material which has substantially greater elasticity than the material of construction of the elements 28 and 30. However, it is to be understood that the elasticity of the material of the elements 36 and 38 is to be substantially more rigid than the lead material of the projectile 16.

It is to be noted that the aft edge 44 of the elements 28, 30, 36 and 38 are in substantial alignment and also in alignment with the plane of the base 46 of the projectile 16. The surface area of the aft edge 44 of the elements 36 and 38 are to comprise approximately fifty percent of the entire aft surface area which includes the surface area of the base 46 and the surface area of the edge 44 of the elements 28, 30, 36 and 38. The reason for the criticality of the area size is so that the forces which are transmitted through the elements 36 and 38 of the second set 26 are sufficient to transmit adequate radial forces through the conical interconnection between the first set 24 and the second set 26. The radial forces must be such so as to supply adequate resisting forces to the aft end of the projectile 16 so as to prevent the aft end of the projectile 16 from enlarging due to the great accelerating stresses which will inherently be encountered. It is to be understood that the exact area arrangement of the aft edge 44 is a matter of choice or design and is to be considered to be determined experimentally considering the following factors: 1. The materials of construction of both the first set and second set. 2. The angle of the conical interconnection between the first set and the second set. It is desired that this angle be maintained small so a substantial area contact is established between the separate sets. In actual practice an angle of 10 from the longitudinal axis of the projectile is most satisfactory. 3. The material of construction of the projectile 14. 4. The size of the projectile 16 considered in view of the size of the bore 20. 5. The velocity at which the projectile 16 is to be launched. In other words, the area of aft edge 44 of the elements 36 and 38 could be substantially increased or substantially decreased and not to be held at the foregoing 50 percent relationship.

Referring particularly to FIGS. 6 and 7 of the drawing, there is shown a second embodiment 48 of the sabot of this invention. The second embodiment 48 includes a first set 50 of half shells and a second set 52 of half shells. In a manner similar to as previously described, a first set of half shells 50 includes elements 54 and 56 which are adapted to surround in a snug fitting manner the projectile 58. The second set 52 of half shells comprises elements 60 and 62 which are adapted to surround in a tight fitting manner the aft section of the first set 50. The interconnection between the first set 50 and the second set 52 is similarly a conical interconnection 64. A plug 66 extends from the first set 50 aft of the base 68 of the projectile 58 with such being conducted through an opening 70 within the second set 52. The connection between the plug 66 and the second set 52 is to longitudinally restrain the second set 52 when in cooperation with the first set 50. The aft surface area of the second set 52 is to similarly comprise approximately 50 percent of the total aft surface area. As a result, sufficient radial forces are being supplied to the conical interconnection 64 to prevent enlargement of the aft end of the projectile 58. It is to be noted that when employing the second embodiment 48, the base 68 of the projectile 58 is not directly exposed to the expanding gases of the cartridge 10). It is to be understood that with the second embodiment 48, the

sabot of this invention will be similarly discarded upon the sabot and projectile leaving the muzzle of a gun.

The main purpose of the sabot of this invention is to provide for launching sub-caliber copper jacketed lead (or pure lead) bullets from larger bore guns. However, it is to be noted that the muzzle velocities are on the order of percent higher for the projectile, which is surrounded by the sabot of this invention than that obtainable by the normal sized projectile for which the gun was designed to operate. As an example, the highest powered 22 caliber rifle is the 220 Swift. This rifle fires a 52 grain bullet with a muzzle velocity of 4,000 feet per second. The making of this rifle has been discontinued because the barrels would not last more than a few hundred shots .due to erosion. This same projectile can be fired from a 30-06 rifle with a discarding sabot of this invention at a muzzle velocity of 4,300 feet per second with a much lower chamber pressure and negligible barrel erosion. Additionally, the highest powered 30 caliber rifle is the 300 Weatherby magnum. It will fire a 180 bullet at 3,200 feet per second with a chamber pressure of 58,000 psi. Using the discarding sabot of this invention, a 45 caliber Weatherby rifle will fire the same 30 caliber projectile at 3,700 feet per second with the same chamber pressure. The 45 caliber rifle is designed to fire a 500 grain bullet at 2,700 feet per second but such bullets are very poor aerodynamically. Thus, such bullets have a very short lethal range. At a range of 300 yards the aerodynamically efficient 300 caliber bullet, which has been fired by means of the sabot of this invention, has a greater remaining kinetic energy than the 45 caliber bullet at the same distance.

We claim:

1. In combination with a soft metal projectile, said projectile to be launched through the bore of the barrel of a firearm, said projectile having a base to which is to be applied expanding gaseous pressure, a projectile sabot comprising:

a first set of half shells to surround a portion of said projectile in a tight fitting manner, the aft edge of said first set to be in substantial alignment with said base of said projectile and subjected directly to said expanding gaseous pressure; and

a second set of half shells to surround a portion of said first set and be in continuous contact therewith, the aft edge of said second set to be in substantial alignment with said base and said aft edge of said first set and subjected directly to said expanding gaseous pressure.

2. The combination as defined within claim 1 wherein:

the surface area of said aft edge of said second set comprises approximately fifty percent of the entire aft surface area including the area of said base.

3. The combination as defined in claim 2 wherein:

said first set having an aft section and a forward section, said second set to surround said first set in said aft section.

4. The combination as defined in claim 1 wherein:

said second set being in contact with said first set and establishing a conical connection therebetween, said conical interconnection being so the cone diameter decreases as said interconnection approaches said aft edge.

5. The combination as defined in claim 1 wherein:

the material of construction of said first set being substantially non-elastic and having extremely high strength characteristics, the material of construction of said second set having substantial elasticity as compared to the material of construction of said first set.

6. In combination with a projectile, said projectile to be launched through the bore of the barrel of a firearm, said projectile having a base to which is to be applied expanding gaseous pressure, a projectile sabot comprising:

a first set of half shells to surround a portion of said projectile in a tight fitting manner, the aft edge of said first set to be in substantial alignment with said base of said projectile;

a second set of half shells to surround a portion of said first set, the aft edge of said second set to be in substantial alignment with said base and said aft edge of said first set;

the surface area of said aft edge of said second set comprises approximately fifty percent of the entire aft surface area including the area of said base;

said first set having an aft section and a forward section, said second set to surround said first set in said aft section;

said second set being in contact with said first set and establishing a conical connection therebetween, said conical interconnection being so the cone diameter decreases as said interconnection approaches said aft edge.

7. The combination of claim 6 wherein:

the angle of said conical interconnection being approximately 10 in respect to the longitudinal axis of said projectile.

8. The combination as defined in claim 6 wherein:

the material of construction of said first set being substantially non-elastic and having extremely high strength characteristics, the material of construction of said second set having substantial elasticity as compared to the material of construction of said first set.

9. A projectile sabot comprising:

a first set of shells, said first set of shells to matingly cooperate together to form a substantially continuous tubular element, said first set cooperating to form an enlarged plug extending rearwardly of said first set of shells; and

a second set of shells to surround a portion of said first set, said second set of shells to cooperate together to form a substantially continuous tubular element, the interconnection between said sets forming approximately an angle of ten degrees with respect to the longitudinal axis of said first set of shells, said second set of shells cooperating to form an opening in the aft end of said second set, said enlarged plug to extend through said opening.

10. A sabot as defined in claim 9 wherein:

said plug having a necked down section, said first set of shells to interfit within said necked down sec.-

tion.

* i #1 it 

1. In combination with a soft metal projectile, said projectile to be launched through the bore of the barrel of a firearm, said projectile having a base to which is to be applied expanding gaseous pressure, a projectile sabot comprising: a first set of half shells to surround a portion of said projectile in a tight fitting manner, the aft edge of said first set to be in substantial alignment with said base of said projectile and subjected directly to said expanding gaseous pressure; and a second set of half shells to surround a portion of said first set and be in continuous contact therewith, the aft edge of said second set to be in substantial alignment with said base and said aft edge of said first set and subjected directly to said expanding gaseous pressure.
 2. The combination as defined within claim 1 wherein: the surface area of said aft edge of said second set comprises approximately fifty percent of the entire aft surface area including the area of said base.
 3. The combination as defined in claim 2 wherein: said first set having an aft section and a forward section, said second set to surround said first set in said aft section.
 4. The combination as defined in claim 1 wherein: said second set being in contact with said first set and establishing a conical connection therebetween, said conical interconnection being so the cone diameter decreases as said interconnection approaches said aft edge.
 5. The combination as defined in claim 1 wherein: the material of construction of said first set being substantially non-elastic and having extremely high strength characteristics, the material of construction of said second set having substantial elasticity as compared to the material of construction of said first set.
 6. In combination with a projectile, said projectile to be launched through the bore of the barrel of a firearm, said projectile having a base to which is to be applied expanding gaseous pressure, a projectile sabot comprising: a first set of half shells to surround a portion of said projectile in a tight fitting manner, the aft edge of said first set to be in substantial alignment with said base of said projectile; a second set of half shells to surround a portion of said first set, the aft edge of said second set to be in substantial alignment with said base and said aft edge of said first set; the surface area of said aft edge of said second set comprises approximately fifty percent of the entire aft surface area including the area of said base; said first set having an aft section and a forward section, said second set to surround said first set in said aft section; said second set being in contact with said first set and establishing a conical connection therebetween, said conical interconnection being so the cone diameter decreases as said interconnection approaches said aft edge.
 7. The combination of claim 6 wherein: the angle of said conical interconnection being approximately 10* in respect to the longitudinal axis of said projectile.
 8. The combination as defined in claim 6 wherein: the material of construction of said first set being substantially non-elastic and having extremely high strength characteristics, the material of construction of said second set having substantial elasticity as compared to the material of construction of said first set.
 9. A projectile sabot comprising: a first set of shells, said first set of shells to matingly cooperate together to form a substantially continuous tubular element, said first set cooperating to form an enlarged plug extending rearwardly of said first set of shells; and a second set of shells to surround a portion of said first set, said second set of shells to cooperate together to form a substantially continuous tubular element, the interconnection between said sets forming approximately an angle of ten degrees with respect to the longitudinal axis of said first set of shells, said second set of shells cooperating to form an opening in the aft end of said second set, said enlarged plug to extend through said opening.
 10. A sabot as defined in claim 9 wherein: said plug having a necked down section, said first set of shells to interfit within said necked down section. 